Applications have also been filed directed to a power unit convertible into a jack, a lift bridge, a lift arm assembly, and a safety mechanism, as described in the present specification.
The invention relates to a device for lifting and supporting an object i.e. a corner of an automobile; particularly to a two part jacking system including a power unit that can be used to place and elevate a jack stand. The inventor of the present invention is a pioneer of the two part jacking system holding numerous issued patents for a two part jacking system and related products and processes as described below.
Briefly, the two part jacking system consists of a power unit and a set of separate mechanical jack stands. Examples of the two part jacking system and power unit are described in detail in Re.32,715 and U.S. Pat. No. 4,589,630. Some examples of the jack stands are described in detail in U.S. Pat. Nos. 4,553,772; 4,490,264; 5,110,089; 5,183,235 and 5,379,974. The stands are capable of being vertically extended and retracted from the garage floor or road surface and, when extended, can be locked in place at any desired position by a ratchet and pawl assembly. The power unit has a mobile chassis adapted to carry a plurality of the jack stands, and has a pair of lift arms adapted to mate with the outermost jack stand for placement and removal.
In use, the mobile power unit is operated entirely from its handle. It is maneuvered under a vehicle to place a jack stand in a desired location for lift and supporting the vehicle. The power unit is activated from the handle, and this jack stand is then vertically extended to the desired height, thus lift the vehicle on the stand. By operating the controls at the end of the handle, the operator can cause the power unit to disengage from the stand, and the stand will remain locked in its extended supporting position under the vehicle. In this manner, the vehicle is raised and supported on a separate mechanical stand without transferring the vehicle from a jack to a stand and without the operator placing any part of his body under the vehicle or having to touch the stand itself. After the stand is raised and locked in place to support the vehicle or other load in a lifted position, the power unit lift arms are lowered and the power unit is disengaged from the stand and pulled away, leaving the stand in position supporting the load. Another jack stand, carried within the chassis, is automatically transferred to the forward end the chassis for placement at another desired location of the vehicle or for use to lift and support another vehicle.
To lower the vehicle and remove the stand, the power unit is maneuvered to reengage with the stand. The engagement causes any existing jack stands carried within the chassis to be automatically transferred rearward within the chassis. By manually operating a control at the end of the handle, the user can cause the power unit to reengage with the stand, and to disengage the ratchet locking mechanism of the stand and lower the stand to its original position. The power unit remains engaged with the stand and can be pulled away from the vehicle with the stand carried within the chassis.
The original power units were adapted to carry one or two jack stands within the chassis for consumer use; and up to four jack stands within the chassis for commercial use. Additional jack stands could be purchased and arranged at various stations on the garage floor to reload the power unit, so that a single power unit could be utilized to efficiently place and actuate numerous jack stands. However, it was found that many commercial users would utilize all of their available jack stands, and the power unit was thereafter useless until another jack stand was available to be extracted and reused. It was determined that it would be highly desirable if the power unit could also function as a lift device when no jack stands were available, and when the power unit was separated from the source of jack stands.
It was also discovered that consumer projects usually required only two supports, and it was determined that it would be highly desirable to have a consumer system consisting of one jack stand and a power unit that could also be utilized as a lift and supporting device.
It was also discovered that commercial users routinely provide emergency field service, and the weight and extended chassis length (for carrying four jack stands) was somewhat unwieldy and difficult to be loaded, transported and maneuvered for such emergency field services. It was determined that it would be highly desirable to have a compact commercial power unit for shop use; and that could also efficiently be used as a stand alone lift and supporting device, as well as a power unit for use with a jack stand, for such field service.
The two part system efficiently and effectively eliminates the need to use a cumbersome hydraulic floor jack as a jack stand. However, some consumer and even professional users carelessly and hastily use the hydraulic jack as a supporting device until the project is completed. Hydraulic jacks have suffered from the disadvantage of hydraulic bleed, making performance in supporting a load over an extended period of time, unpredictable and hazardous for the user. It was determined that it would be highly desirable to provide a hydraulic lift device with a reliable mechanical mechanism for securing the lift arm so that it would support the load even upon hydraulic bleed or other failure of the hydraulic lift system.
In view of the foregoing problems and desirable features of a two part lift and supporting system, it is an object of the present invention to provide a power unit for use with a jack stand, that is readily convertible for use directly as a load-lifting jack.
It is another object to provide a power unit that is automatically adapted for use with a jack stand when engaged with a jack stand, and automatically adapted for use as a load-lifting jack when not engaged with a jack stand.
The foregoing objects are accomplished by leveling pads for use with a jack stand power unit that is convertible for use as a lifting jack. The power unit includes a generally rectangular chassis having a forward end and a rearward end containing a pair of parallel lift arms interconnected near the midpoints thereof by a lateral pivot push bar. The lift arms have upper surfaces, forward ends and rearward ends, with the forward ends having horizontal apertures. The rearward ends of the lift arms are pivotally retained within the rearward end of the chassis. A pair of connecting arms acting in parallel have forward ends pivotally connected to the forward end of the chassis and have rearward ends pivotally connected near the midpoint of the respective lift arm coaxial with the push bar.
A hydraulic actuator is mounted on the chassis having a forward end connected to the push bar for elevating the forward ends of the lift arms. A lift bridge comprising a horizontally oriented rectangular plate has forward end rearward ends, left and right sides, top and bottom surfaces and is adapted to be positioned to bridge between the forward ends of the lift arms, and further adapted to be positioned away from the forward ends of the lift arms.
The leveling pad comprises a vertically oriented rectangular plate having an upper surface aligned with the upper surface of the lift arm, a forward end and a central horizontal aperture and is pivotally attached coaxial with the aperture of the respective lift arm. The pad has a guide flange extending horizontally from the upper surface adapted to engage the respective side of the lift bridge. The plate has a lever arm extending forward and downward from the forward end of the plate, and has a length of about half the length of the connecting arm. a connecting rod interconnecting the end of the lever arm to a point on the pivotal connecting arm, so that as the angle between the lift arm and the connecting arm increases, the angle between the lift arm and the lever arm decreases so that the upper surface of the leveling member remains horizontal during the elevation of the lift arm. The leveling pads provide a level platform on the forward ends of the lift arms with an opening for engaging the lift collar of a jack stand, or for engaging the lift bridge.